1. Field of the Invention
The present invention generally relates to electromagnetic relays. More specifically, the present invention relates to an electromagnetic relay configured to turn on or off electric power of an electrical device for home or industrial use.
2. Description of the Related Art
Under conditions where a voltage applied to a contact configured to perform opening and closing operations in an electromagnetic relay is high and an amount of an electric current flowing into the contact is large, when a fixing contact and a movable contact forming the contact become separated from each other from a state where the fixing contact and the movable contact come in contact with each other or when the fixing contact and the movable contact come in contact with each other from a state where the fixing contact and the movable contact forming the contact are separated from each other, an arc may be generated in a case where the voltage becomes greater than a minimum arc voltage or the electrical current becomes greater than a minimum arc electrical current.
The arc is a phenomenon where an electrical current flows in an air gap between surfaces of the fixing contact and the movable contact in a state where an electrical load is applied between the fixing contact and the movable contact. The arc starts when an electron moves from a cathode to an anode by flowing across the air gap. The electron collides with a molecule of air accompanying movement of the electron in the air gap so that ionization occurs. The electron reaches the anode so that the anode is heated. Thereby, a cation is discharged to the air gap from the anode. As a result of this, the cation collides with the cathode so that the cathode is heated.
Thus, heat generated at the anode and the cathode may cause evaporation of the molecules forming the anode and the cathode so that the wear at the surfaces of both the fixing contact and the movable contact may be increased. Accordingly, it may be required to inhibit the wear due to the arcing as much as possible. Such an electromagnetic relay configured to inhibit the wear due to the arcing has been suggested in, for example, Japanese Laid Open Patent Application Publication No. 2006-196372.
In the electromagnetic relay described in Japanese Laid Open Patent Application Publication No. 2006-196372, a characteristic of the arc which is the same as a magnetic characteristic of the electrical current is used. With this structure, by a magnetic flux due to a magnet provided at a movable spring which urges in a direction to separate the movable contact from the fixing contact, the arc can be bent and deflected. Hence, heating and the wear of the contact can be inhibited. However, in this structure, the arc is transferred to the movable spring. Therefore, this structure may cause the wear of the movable spring so that the opening and closing operations of the contact may be influenced. In addition, the magnetic flux of the magnet is fixed in a single direction. Therefore, in a case where the contact of an alternating current is opened or closed, since a direction of the arc is periodically changed, it may be, depending on a way of using the magnet, difficult to control the direction of the arc.
Here, in a case where the contact is opened or closed and the voltage and the electrical current are high, in order to increase durability against the wear of the contact, the volume of the contact may be increased; plural of the contacts may be provided; or the air gap between the contacts may be increased. As a result, the external dimensions of the electromagnetic relay may be increased so that the manufacturing cost may be increased.